Many investigators have suggested a correlation between anatomical remodelling and functional recovery based upon observations that both phenomena are more prominent after neonatal brain damage. The proposed experiments address the most important yet least understood questions pertaining to the basic mechanisms and functional significance of remodelling. The initial experiments are designed to ascertain whether sprouting systems retain the same specificity of connections as is present within normally developing pathways. Accordingly, corticopontine sprouting to the contralateral pontine gray will be examined to determine if the aberrant projections maintain the appropriate somatotopy of projection as seen in the normal ipsilateral distribution. Additional studies will examine whether aberrant projections, which in the case of the spinovestibular and spinocerebellar systems distribute to functionally related areas after ablation of their normal target by neonatal hemicerebellectomy, can be 'forced' to project to areas with little functional association. Functional correlations with plasticity will be examined in terms of methods based on the selective uptake of radioactive 2-deoxyglucose as a market for metabolic activity. It is speculated that areas with anomalous innervation may exhibit altered metabolic activity in comparison to controls. Recent evidence suggests that the noradrenergic (NA) system may play an important role in the regulation of plasticity within our neurotransmitter systems. This possibility will be tested by examining corticopontine and corticospinal plasticity following the neonatal administration of 6-OHDA. The administration of this drug increases the density of brainstem and cerebellar NA terminals and decreases NA projections within the cortex and spinal cord and thus facilitates an analysis of the effects of NA alterations on anatomical remodelling. Further study is designed to examine whether the vestibular complex which is normally devoid of NA fibers will receive aberrant NA innervation concomitant with spinovestibular sprouting after neonatal hemicerebellectomy.